1. Field of the Invention
This invention relates to a novel method for conducting chemical reactions involving one or more reactants maintained in a liquid phase reaction medium to form at least one product comprising a solid which accumulates in the reaction zone on particles of either the same or different composition by a nucleated growth mechanism. It provides a method whereby the reaction and the separation of the resulting product occurs in a single reaction-separation zone.
This invention also relates to a novel method for upgrading hydrocarbonaceous materials such as coal, petroleum derived material such as residual oils and heavy crudes, shale oils and tar sand extracts. More particularly, this aspect of the invention relates to a novel method whereby such hydrocarbonaceous materials may be continuously coked in a controlled manner to produce and separate a solid coke product. This aspect of the invention further relates to the conversion of solid carbonaceous materials to low sulfur liquid and solid fuels, particularly to an improved coal conversion process wherein dissolution of coal in a coal dissolution solvent and separation of undissolved solids and by-product coke from the solvent/coal extract mixture is achieved in a single step.
Another aspect of this invention relates to a method for carrying out polymerization reactions and particularly relates to a method for the polymerization of olefins employing Ziegler-type catalysts.
A still further aspect of this invention relates to a continuous method for the synthesis of zeolites having a substantially uniform crystal size.
2. Description of the Prior Art
Centrifugal reactors or reactors having a flow scheme characterized by a spiral flow of a fluid phase reaction medium are generally known. For example, U.S. Pat. No. 2,259,717 discloses a process for softening water by precipitating "hardness constituents" on cores of contact material which comprises introducing water into the lower portion of an elongated chamber containing granular contact material, adding a softening agent to the water substantially simultaneously with said introduction, and flowing the water containing said agent upwardly through said contact material at a velocity high enough to agitate and maintain the granular material in suspension but insufficient to carry the contact material out of the chamber. The patent suggests that the water be introduced into the chamber at such an angle as to flow upwardly into the chamber with a swirling motion. The chamber is preferably in the shape of an inverted, truncated cone. An advantage of the U.S. Pat. No. 2,259,717 process is said to be that precipitated hardness is collected in the form of enlarged granules rather than watery sludge and these granules can be more readily separated from water for disposal. The granular material grows in size as successive adherent layers of precipitates deposit on the surface. When the granular material reaches such a size that the upper surface of the expanded bed of granular particles nearly reaches the point in the upper portion of the reactor where the softened water is withdrawn, feed to the unit is discontinued, the solid particles are removed and fresh granular contact material is added to the unit. Thus, the operation is semi-continuous with the contact material being added on a periodic basis. Although the U.S. Pat. No. 2,259,717 process is particularly directed to the softening of water, the patent indicates that it is broadly applicable to the precipitation of electrolytes from solutions of the electrolyte by addition of a precipitant to the solution and flowing the resulting mixture through a bed of granular contact material as described above.
Various processes are known for thermally upgrading hydrocarbonaceous materials including thermal cracking, thermal reforming, vis-breaking, and coking. Known coking processes include delayed coking, continuous contact coking and fluid coking. In delayed coking processes a heavy fuel oil or gas oil is heated to a temperature above 900.degree. F. and is then permitted to dissociate into coke and light overhead by "soaking" in a coke drum. This operation is continued until the drum is filled with coke, after which it is taken offstream and the coke is broken out by mechanical or hydraulic means. Continuous contact coking is a process wherein a hydrocarbon feedstock is preheated to 750.degree.-800.degree. F. in a conventional tubular preheater. The hot oil is brought into immediate contact with a large quantity of hot circulating coke in the form of rounded lumps in the 1/4 inch to the 3/4 inch size range. This carrier coke is usually formed in the process itself. It is found that the hydrocarbon oil wets the solid particles quite uniformly in very thin layers. From the point of contact the hot, wetted coke is permitted to travel by gravity through the reactor zone in which it is given a soaking time of 15 to 40 minutes. The freely moving particles pass through a sealing zone into a heater where they are once again raised to proper recirculation temperature by exposure to radiative and some convective heating. Then the hot coke is returned to the point of contact with the hydrocarbon stock. A portion of the coke particles is continuously removed from the system as product. The removal generally takes place via a sizing unit so that the granules below 3/4 inch may be returned to the process. In fluid coke processes the feed is sprayed into a fluidized hot bed of coke particles. The pellets of coke circulate continuously from the reactor bed into a fluidized burner bed where enough coke is burned to heat the remaining bulk of the pellets to about 1150.degree. F. and the particles are then sent back to the reactor. Some of the coke particles are continuously removed and they are usually pulverized for use as power plant fuel. Fluid bed coking process is difficult to operate at relatively low temperatures except at very low feed rates due to the sticky feed causing loss of fluidity in the bed of solids.
A common characteristic of all of the foregoing thermal upgrading methods wherein a coke byproduct is formed is that they require large and expensive equipment. Moreover, delayed coking is a batch process and removing coke from the drums is an expensive and difficult operation. Both the moving bed and fluid bed processes require separate solids classification and separation equipment for the coke product. None of these processes has provided a highly effective and controllable low cost process for the conversion of hydrocarbonaceous materials into more valuable, lower boiling products.
A further problem encountered in liquid phase thermal upgrading processes is the presence of particles dispersed in the liquid product, the presence of which lowers the quality and economic value of the liquid product. A particularly notable example of this is the liquefaction of normally solid carbonaceous material such as coal.
In solvent refining processes for the conversion of coal to clean liquid or solid fuels, coal is heated in an organic solvent often in the presence of hydrogen to a temperature just sufficient to dissolve most of the organic material in the coal. Following this treatment the products are separated to yield a high boiling extract containing liquid hydrocarbons derived from coal in a solid phase composed of insoluble coal residues. The insoluble coal residues are sometimes only partially separated from the residue to permit the recovery of the residue in the form of a flowable slurry. The extract may then be recovered as a relatively low ash, low sulfur product resembling asphalt in appearance or, alternatively, the extract may then be separated and subjected to catalytic cracking or other refining operations for conversion of the high boiling material into lower boiling hydrocarbons. The solids separated from the extract have been subjected to a low temperature carbonization treatment for the production of additional liquid products which are useful as fuel. Processes which are exemplary of solvent refining processes are disclosed in U.S. Pat. Nos. 3,518,182, 3,520,794, 3,523,886, 3,748,254, 3,841,991 and 3,920,418.
The fundamental reaction of the solvent refining processes is depolymerization in solution of a major portion of the coal in a hydrogen donor solvent (usually having an aromatic composition) as a result of hydrogen transfer to the coal from the donor solvent. Subsequent steps separate the reaction products and recover solvent from the extract and from the solid residue. The separation of undissolved coal residue and ash from the solvent-extract solution is a most critical step in preparing clean fuels from coal by the solvent refining process and improved methods for their separation are needed.
It is well known that alpha olefins can be polymerized at low temperatures and pressures in the presence of certain catalyst compositions. Such processes are conducted at temperatures below about 150.degree. C. and pressures below about 500 psi. These methods are further characterized by the presence of low pressure or "Ziegler" catalysts. In general, these catalysts can be obtained by treating a compound of the metal of Group IVB, VB, VI, VII or VIII with a metal of Group I, II or III in metallic hydride or organo metallic form. Monomers suitable for low pressure polymerization include ethylene, butylene, propylene, styrene and other alpha olefins. The polymer produced is often referred to as "crystalline", "low-pressure", or "linear". It is highly desirable that the product polymer should have the narrowest possible particle size distribution and good free-flowing properties.
For example, U.S. Pat. No. 2,971,951 discloses a process wherein a solid particulate catalyst is suspended in an upward-flowing, liquid phase stream of an olefin which is diluted with a suitable diluent hydrocarbon and effecting polymerization of the olefin to solid, non-tacky polymer in particulate form by contact with the catalyst under suitable reaction conditions which promote the formation and growth of solid particles of polymer in suspension; causing solid particles of polymer having a predetermined minimum size to settle against the stream of hydrocarbons; and recovering the settled particles. In one embodiment of the U.S. Pat. No. 2,971,951, an apparatus is disclosed which comprises a reaction chamber having a substantially frusto-conical configuration positioned above and in open communication with a washing chamber, also having a frusto-conical configuration. The olefin and the inert liquid hydrocarbon diluent are separately or simultaneously introduced through a plurality of jets or spargers located near the joinder of the reaction and washing chambers. Particulate catalyst is continuously added near the top of the reaction zone and is maintained therein as a dense fluidized bed or mass of free-falling particles by the upward velocity of the olefin/diluent mixture. As the polymerization reaction in the reaction zone proceeds, particulate solid non-tacky polymer having a particle size exceeding the maximum size fluidizable in the olefin/diluent mixture are formed and settled out of the reaction zone, passed through the washing zone and are recovered.
U.S. Pat. No. 3,687,919 discloses a process for producing spherical particles of ethylenic monomers with controlled size distribution by a two-stage, polymerization method wherein a portion of the monomer is prepolymerized with turbulent agitation, the prepolymerized monomer is mixed with a large quantity of additional monomer and the resulting mixture is slowly polymerized with mild agitation. The quantity of monomer prepolymerized and the speed of agitation during the prepolymerization is said to serve as control on size distribution of the final product.
The synthesis of zeolites is generally accomplished by methods wherein aqueous solutions of template-inducing species such as specific inorganic or organic cations or organic amines and soluble sources of silica and alumina are reacted at temperatures between about 20.degree. to 250.degree. C. at atmospheric pressure to from the desired crystalline zeolite product. The zeolite crystals are then separated from the mother liquor and washed. The concentrations of soluble reactants and the temperature of the reaction are adjusted to give the desired SiO.sub.2 /Al.sub.2 O.sub.3 ratio in the product and the desired rate of crystal growth. The reaction mixture is initially continuously or periodically stirred to insure homogeneity. After this mixing, agitation may be stopped as it is unnecessary to agitate the reaction mass during the formation and crystallization of the zeolite although mixing during such latter stages has not been found to be detrimental.